Electron-beam generated air plasma: Measurement of ozone and electron density

An electron-beam is used to produce air plasma that is studied experimentally through several diagnostic methods. These include an ozone absorption system, an rf phase measurement system, and emission spectroscopy. The electron beam is produced by an electron gun producing single pulses at 100-keV, 10-ms duration, and 5.6-mA current. The beam is injected into a test cell through a 12.7-mum aluminum foil separating the electron gun from the test cell. The cell pressure is varied from 1 mT to 600 T. N2 Second Positive emissions at 337.1 nm are observed 2 cm from the aluminum foil window. Volumetric ionization and dissociation of air molecules 25 cm from the foil window at the midplane of the test cell results in ozone generation and plasma electron generation. Optical absorption spectroscopy at 255 nm is used to observe ozone, and a 10 GHz rf phase measurements system quantifies electron density. Ozone production and rf phase shift are interpreted using an air chemistry code to estimate the volumetric ionization rate. These measurements are compared with the model, and an estimate of the power required to generate and sustain the plasma is extracted from the rf phase measurements.